Interlock is a non-profit organization that provides space for its members and the local community to develop and share their interests in science, technology, art, and culture.

How to 3D-print a Handle and Trigger for the 3Doodler (and to make it look like a Phaser).

The 3Doodler  is a hand-held 3D printer!  The company is taking pre-orders now for April delivery.  Last summer it was a “crowd-funded” Kickstarter project, and we invested in it.  Our reward for sponsoring this clever invention was to receive our very own pre-production device in January. It is kind of a cross between a hot-glue gun and a 3D printer.

Doodler 1

Unlike a glue-gun that melts a stick of rubbery plastic to glue things together, the 3Doodler can melt a 3mm filament of ABS (a kind of plastic that many things are made of) and extrudes it into a softened web-like thread that can draw up off of the paper in the open air and into almost any shape you can imagine.  While it is intended to be used for making plastic objects by drawing 3-dimensional doodles, we use it primarily to fix plastic objects that have broken or to hack plastic things by adding features to them.  But more about that in a later blog post.

Now we would like to tell you how the team of MacGyvrBot and Skip have found a way to make this great product even better!

Doodler 2

We used Tinkercad to hack-up a model for a Handle and Trigger mechanism, and then we published the design at so that anyone with access to a 3D printer can download the .stl files and make a Phaser Handle for 3Doodler of their own.

or you can just click these links to download the 3 files

Handle ,



This kind of sharing is called open-source hardware design, and the practice allows people to build on each other’s ideas.  You can also use Tinkercad to copy this design at  and modify it with your own ideas.  Progress is faster this way, so open-source design is the best way to get the most out of 3D printing.

Doodler 3

This Phaser Handle makes the 3Doodler look cool (like the Star Trek weapon), but it also makes doodling more comfortable (especially for people with small hands).  The makers of the 3Doodler obviously have plans for making a handle, because they provided a handy mounting bracket with threaded holes for M3 screws.  But we couldn’t wait!

The handle alone is beneficial, but using the trigger with the handle keeps the hand more relaxed during extended doodling.

Doodler 4

The Phaser Handle is attached to the 3Doodler with a pair of M3 x 10mm screws (any head design).  The trigger attaches to the handle with a pair of small flat head screws (such as 6-32 x 3/8 inch or M3 x 6mm) serving as hinge pins.  The screws are available at Lowes and Home Depot.

Doodler 5

The handle is hollow to allow access to a mounting screw (rather than having an infill of plastic in a sparse honeycomb pattern).  If your printer drops a few threads while bridging across the top of the handle, just let it finish the job.  Chances are it will recover before the top layer is reached.  If it fails, you may have to adjust your slicer settings (such as slowing the speed for bridges) and try again.

In our next blog post, we will show you how to use the 3Doodler itself to update the Phaser Handle.   The exercise will be a good demonstration of using the 3Doodler to hack an existing product.

Stay tuned!

from on March 10th, 2014Comments0 Comments

Repairing the audio on a Pac-Man arcade board

I got this knockoff JAMMA Ms Pac-Man arcade board many years back.  It’s got two ROMs instead of the authentic board’s 6 (9 for Ms Pac), and is substantially smaller than the “real thing”.  The only issue is that the audio is poor… REALLY poor.  It makes sounds but they’re… wrong and noisy.

I took over some desk space at Interlock and got to work.  (I should note that the beverages you can see here are other people’s, not mine. ;)

I traced the audio circuit on a real Pac-Man schematic (seen on my laptop’s monitor), and buzzed it out on the Yenox board to try to corrolate the two.

I had to trace four similar paths from a quad flip-flop, through a quad bidirecional switch, to the audio output.  It got really confusing at times, and took me probably a bit longer than it should have.  For the most part, they were pin-for-pin correct as far as how they were wired.  These chips have the same device (eg, a flip flop, or a logic gate) repeated 4 or 6 times.  In some cases here, the Yenox board had a different one of these devices hooked up, which added to the confusion.

This portion of the circuit uses 8 resistors to make a digital-to-analog converter. These generally work by having different resistance levels, usually something like multiples of eachother, eg,  10k ohm, 22k ohm, 47k ohm then 100kohm.  I traced out all of the lines on the Yenox board and I found out that not only were the resistors in the wrong order on the board, but they were also wildly wrong (47 ohm instead of 4.7k ohm), which you can see in this table I made:


You can see these resistors here on the Yenox board, right next to the JAMMA connector.  They start from the left with R1 (my notation.)  The printing on the board completely matched the resistance values that sat on them, so it’s obvious that the engineer who made this board seriously screwed it up in the design stage.

I replaced resistors R3 – R7.  I put them in with the gold band closer to the JAMMA connector, rather than the other way around.

And now it sounds near-perfect.  There’s a little bit of popping left, but I was getting tired and decided to head home for the night.  I’ll hook it up to an oscilloscope at some point and see if i can figure out which line is causing problems.

For what it’s worth, I also did the same as this on the video path DAC, seen in the above picture as the next three groups of resistors.  In the above, the group of four and then the group of five are for audio, then the next group of three is for the “red”, next three for “green”, next two for “blue”, and the remaining two are for the sync.  Again, there were some 47 ohm resistors mixed in, and notice two of the three in the “green” section are identical (red-red-brown)… which is surely wrong.  Color is now perfect on the board too!

from on February 12th, 2014Comments0 Comments

Updating my JAMMA test rig

Many years back, I hooked up a spare JAMMA harness to an old PC power supply, a monitor and some repurposed joystick pads.  (JAMMA is a standard connector size and pinout to hook up arcade game boards into arcade cabinets.  Most of my arcade game boards are either natively Jamma (Mortal Kombat, Klax, Block-out) or I have adapters to hook them up using JAMMA.  (Dig-Dug, Pac-Man, etc)).  One board that I’ve been using with it recently is a knockoff Ms. Pac-Man board, seen in these photos.

Being that I’ve been wanting to work on arcadey projects recently at Interlock, I decided to make this thing a lot less janky.

The harness/rig I have was always kind of a hack.  The video and audio wires terminated in a small box with some knobs which were meant to attenuate the signal but never really worked right.  The power switch was on this cord that came out and was weirdly fastened to the side of the power supply.  I decided to clean this up while at Interlock for open night.

 It turns out that I happened to have the right 6 pin DIN connector for this old RGB monitor (basically a Commodore Amiga 1084 clone).   So I wired up Red, Green, Blue, and Ground directly to the correct pins on it.  JAMMA spits out composite video, but this monitor takes in Horizontal and Vertical sync.  I knew that some monitors would take in composite sync on their Vertical Sync line, so I tried that… and it worked! Huzzah.

The only video issue now is that the game boards put out video that’s slightly too hot/too high a voltage, so I should put attenuation resistors inside the din connector or something…

Even though the JAMMA interface spits out amplified audio, I decided to hook up an RCA plug on the audio lines anyway, to plug it into the line-level in on the monitor.  As long as I’m careful it will be fine.

And here it is being driven by my Yenox Ms Pac-Man board with the “Horizontal Ms Pac” rom hack.  You can see the power switch sticking out of the side of the power supply there.  It’s not the most optimal thing ever, but it’s substantially cleaner than before.  Perhaps I’ll replace that switch with a nice carling switch in the future.  I’ll need this test rig for the next task, which is fixing the audio on this board.  It sounds horrid…

from on January 30th, 2014Comments0 Comments